IDDM is a dynamic process involving the destruction of the pancreatic islet cells by lymphocytes. The process can be appreciated, quantified and characterized visually by histological techniques. The main goal of the histology core is to provide reproducible high quality histochemistry techniques to the investigators in this program project. The principle investigator of the histology core has much experience in the area of pancreatic histology. The core will accept both fixed and frozen tissue from investigators and produce high quality histological sections stained with hematoxylin and eosin. The core will also perform immunocytochemistry studies with antibodies to the pancreatic islet hormones and leukocyte subsets for the investigators in the program. The core director will be available to review slides with the investigators and postdocs involved in the research in this program. The investigators in this program project will provide the workload of the core. When the workload becomes overwhelming, the core direction, in consultation with the program director will prioritize the work schedule as best suits the overall goals of this program project. The core will keep abreast of new techniques and newly available reagents in the histochemistry/immunocytochemistry field, establishing these techniques for use of investigators in the program. The histology core is an important central resource for the investigators in this program project, enabling the dynamic cellular processes that occur in IDDM to be visualized and interpreted.